1. Field of the Invention
This invention relates to electro-optic sampling oscilloscopes which use electro-optic probes to produce waveforms representative of measured signals. Herein, the electro-optic probes detect polarization states of laser beams (or laser pulses) incident on electro-optic crystals, which are placed under effects of electric fields caused by the measured signals.
2. Description of the Related Art
Conventionally, the electro-optic sampling oscilloscopes are used to provide visual display of waveforms of measured signals by using electro-optic probes, which operate in accordance with the known electro-optical phenomenon as follows:
Electric field caused by the measured signal is connected with an electro-optic crystal, on which laser beams are incident. Thus, it is possible to visually display the waveform of the measured signal in response to polarization states of the laser beams. Herein, the laser beams are made in a pulse-like form by which the measured signal is subjected to sampling. Thus, it is possible to measure the waveform of the measured signal with very high resolution with respect to time.
Engineers pay great attention to the aforementioned electro-optic sampling oscilloscopes (which are abbreviated by xe2x80x9cEOS oscilloscopesxe2x80x9d, for example). This is described in a variety of papers such as the paper entitled xe2x80x9cA High-Impedance Probe Based on Electro-Optic Samplingxe2x80x9d, which is written by Mr. Shinagawa and other members for the Proceedings of 15th Meeting on Lighwave Sensing Technology on pp. 123-129 of the collection of monographic papers for the Institutes of Applied Physics and Lightwave Sensing Technology, which is published on May of the year 1995. Because, as compared with the conventional sampling oscilloscopes using electric probes, the electro-optic sampling oscilloscopes have a variety of technical features, as follows:
(1) Because the EOS oscilloscope does not need the ground line when measuring signals, it is possible to perform measurement with ease.
(2) Because a metal pin (or metal needle tip) located at a tip end of the electro-optic probe is insulated from circuitry, it is possible to actualize a high input impedance, which does not substantially disturb a state of a measured point.
(3) Because the EOS oscilloscope uses optical pulses, it is possible to perform broad-band measurement up to the Giga-Heltz (GHz) order.
By the way, the EOS oscilloscopes display measured data in a simple way, as follows:
That is, the EOS oscilloscope simply displays the waveform of the measured data during the measurement or just after the measurement. Or, the measured data produced by the EOS oscilloscope are input to the personal computer or else, wherein general-purpose software is used to merely display numerical values of the measured data or waveform of the measured data.
As described above, the EOS oscilloscope has a capability to produce the measured data with high precision. However, the conventional technology does not provide an appropriate way of display in which a human operator (e.g., user) is capable of grasping the content of the measured data at a glance. In addition, it does not provide an appropriate environment of display in which the human operator is capable of comparing the measured data and measurement conditions with ease.
It is an object of the invention to provide an electro-optic sampling oscilloscope by which a user is capable of grasping content of measured data at a glance.
It is another object of the invention to provide an electro-optic sampling oscilloscope which provides a user with an appropriate environment of display in which the user is capable of comparing measured data and measurement conditions with ease.
In general, an electro-optic sampling oscilloscope (or EOS oscilloscope) uses an electro-optic probe containing an electro-optic crystal, which is placed under effect of an electric field caused by a measured signal. Laser pulses are supplied to the electro-optic crystal wherein they are subjected to polarization. Then, measurement data representative of a waveform of the measured signal are produced in response to polarization states of the laser pulses and are stored in a measurement data storage.
The EOS oscilloscope of this invention is characterized by providing user friendly display processing. Herein, a user is capable of selecting specific measurement data by using a list of files of multiple measurement data which is displayed on a screen. Then, the EOS oscilloscope displays an outline waveform which is created based on a reduced number of sample points extracted from the selected measurement data. In addition, it is possible to input comments and/or measurement conditions with respect to the measurement data. The comments and/or measurement conditions are stored in the measurement data storage in relation to the measurement data, so that they are adequately displayed on the screen. Further, it is possible to emphasize display of specific items of the measurement conditions, which the user is capable of designating and changing according to needs. Thus, the EOS oscilloscope provides a user friendly visual display for displaying the measurement data, measurement conditions, comments and outline waveforms on the screen.
Using such a visual display, the user is capable of grasping contents of the measurement data at a glance on the screen.